Motor vehicle operators are generally required to negotiate traffic safely when traveling on public roadways. For this reason, cars, trucks and other road-traveling motor vehicles are typically equipped with mirrors positioned both inside and outside the vehicle. The mirrors allow the driver to see a portion of the roadway behind or beside the host vehicle with only a slight shift of the eyes or turn of the driver's head. If other vehicles are visible, the driver will be suitably alerted and in position to avoid making an inappropriate maneuver, such as a lane change.
Being aware of other vehicles is particularly important when changing lanes on the roadway, either to the left or the right. To change lanes safely the driver needs to ascertain beforehand that there is no obstructive vehicle in the adjacent lane. However, for simple reasons of geometry the conventional side view mirrors generally only provide a partial view of the space immediately to the side and towards the back of the host vehicle, which needs to be clear for the host vehicle to change lanes. Accordingly, a space unviewable via the mirrors, commonly called the “blind spot,” is therefore typically checked by the driver physically turning his or her head to the side so that the blind spot space can be viewed directly. When it is confirmed that the space is clear and that there is no other vehicle fast approaching, the driver can maneuver the host vehicle into the desired lane.
Various detection systems have been proposed for detecting objects in a vehicle blind spot region. Many of the proposed detection systems employ various types of sensors for detecting an object and alerting the driver of the host vehicle of the presence of the object in the blind spot region. One example of a detection system for detecting objects emitting thermal radiation in a blind spot of a vehicle is disclosed in U.S. patent application Ser. No. 10/407,507, filed Apr. 5, 2003, now issued as U.S. Pat. No. 6,961,006 and entitled “OBJECT DETECTION FOR A STOPPED VEHICLE,” the entire disclosure of which is hereby incorporated herein by reference. The aforementioned detection approach employs a single thermal detection sensor detecting thermal radiation emitted in a single coverage zone and detects the presence of an object emitting thermal radiation based on a detected temperature radiation when the vehicle is stopped.
Another example of a proposed detection system for detecting objects in a blind spot of a vehicle is disclosed in U.S. Pat. Nos., 5,668,539 and 6,753,766, both of which are hereby incorporated herein by reference. The approaches disclosed in the aforementioned patents generally employ a plurality of infrared (IR) sensors, such as thermopile sensors, to detect changes in a thermal scene along the side of a host vehicle to detect the presence of a thermal emitting object, such as another vehicle (automobile), in the blind spot region of the host vehicle. This prior technique employs identical IR sensors positioned at predetermined locations along the side of the host vehicle to sense thermal temperature in two predetermined locations. Based on the speed of the host vehicle, the amount of time shift that is necessary to have data from the same physical area at the two different location points in time is determined. If there is a temperature increase in one of the thermal images, then it is assumed to be heat emitted from another vehicle. The heat could be heat reflected from the roadway underneath the other vehicle or heat generated at the interface of the roadway and tires of the other vehicle.
Some thermal radiation detectors employ multiple thermal detection sensors each having a separate lens element for receiving and detecting thermal energy in a coverage zone. Another thermal radiation detector is disclosed in U.S. patent application Ser. No. 10/808,835, filed Mar. 25, 2004, now issued as U.S. Pat. No. 7,148,482, and entitled “MULTIPLE SENSOR THERMAL RADIATION DETECTOR AND METHOD,” the entire disclosure of which is hereby incorporated herein by reference. The aforementioned thermal radiation detector employs first and second thermal detection sensors commonly supported in a housing and arranged to detect thermal energy in first and second corresponding coverage zones by receiving thermal energy passing through an optical lens. The optical lens is arranged to direct thermal energy from the first coverage zone to the first thermal detection sensor, and to direct thermal energy from the second coverage zone to the second thermal detection sensor. The optical lens allows for focused thermal energy to be directed onto the corresponding thermal detectors, however, the optical lens approach can be susceptible to introducing thermal noise or drift, and is generally inflexible to change to allow easy use for multiple platform applications.
It is therefore desirable to provide for a cost-effective and compact thermal radiation detector that offers good signal-to-noise detection of thermal radiation in multiple coverage zones. It is further desirable to provide for a multiple zone thermal radiation detector that may be easily employed on a host vehicle for vehicle side detection and is flexible to accommodate changes.